Cusp structures observed by the TRICE 2 sounding rockets and their relationship to the magnetopause reconnection location

On December 8, 2018, the TRICE-2 campaign (Twin Rocket Investigation of Cusp Electrodynamics) successfully launched two sounding rockets with a two-minute time separation. The rockets crossed the Earth's low altitude magnetospheric cusp region at about 1000 and 600 km, respectively. Each rocket carried an electrostatic analyzer, measuring ions within an energy range from ~10 eV/q to ~20keV/q, to observe temporal and/or spatial structures in the cusp which are related to the magnetic reconnection process at the magnetopause. The instruments observed several distinctive cusp steps which may have both, spatial and temporal signatures. In addition, there were several overlapping ion energy dispersions, indicating the presence of multiple reconnection lines at the magnetopause.

About two hours before the rocket launch, the Magnetospheric Multiscale (MMS) spacecraft crossed the magnetopause and observed accelerated ion beams in the boundary layers; the signature of an active reconnection line. The solar wind conditions during the MMS magnetopause crossings were similar to the conditions during the TRICE-2 launch. Using the prediction of the Maximum Magnetic Shear model, we determine the location of the dayside reconnection line and connect the cusp structures observed by TRICE-2 with their dayside entry points for the precipitating ions.